Featured Research

from universities, journals, and other organizations

Let's do the twist: Spiral proteins are efficient gene delivery agents

Date:
December 17, 2011
Source:
University of Illinois at Urbana-Champaign
Summary:
Clinical gene therapy may be one step closer, thanks to a new twist on an old class of molecules. Researchers have demonstrated that short spiral-shaped proteins can efficiently deliver DNA segments to cells, with well-controlled toxicity. Their helical polypeptides far exceeded random-coil polypeptide and even outstripped commercial agents in efficiency, even on some of the hardest cells to transfect: stem cells and fibroblast cells.

Polymers as gene delivery agents. Helical charged polypeptides, left, deliver DNA to the cell by rupturing the endosomal membrane. Random-coil polymers, right, do not rupture the membrane, so the DNA is not released inside the cell.
Credit: Graphic by Nathan Gabrielson

Clinical gene therapy may be one step closer, thanks to a new twist on an old class of molecules.

Related Articles


A group of University of Illinois researchers, led by professors Jianjun Cheng and Fei Wang, have demonstrated that short spiral-shaped proteins can efficiently deliver DNA segments to cells. The team published its work in the journal Angewandte Chemie.

"The main idea is these are new materials that could potentially be used for clinical gene therapy," said Cheng, a professor of materials science and engineering, of chemistry and of bioengineering.

Researchers have been exploring two main pathways for gene delivery: modified viruses and nonviral agents such as synthetic polymers or lipids. The challenge has been to address both toxicity and efficiency. Polypeptides, or short protein chains, are attractive materials because they are biocompatible, fine-tunable and small.

"There are very good in vitrotransfection agents available, but we cannot use them in vivo because of their toxicity or because some of the complexes are too large," Cheng said. "Using our polypeptides, we can control the size down to the 200 nanometer range, which makes it a very interesting delivery system for in vivo applications."

A polypeptide called poly-L-lysine (PLL) was an early contender in gene delivery studies. PLL has positively charged side chains -- molecular structures that stem from each amino acid link in the polypeptide chain -- so it is soluble in the watery cellular environment.

However, PLL gradually fell into disuse because of its limited ability to deliver genes to the inside of cells, a process called transfection, and its high toxicity. Cheng postulated that PLL's low efficiency could be a function of its globular shape, as polypeptides with charged side chains tend to adopt a random coil structure, instead of a more orderly spiral helix.

"We never studied the connections of conformation with transfection efficiency, because we were never able to synthetically make materials containing both cationic charge and a high percentage of helical structures," Cheng said. "This paper demonstrated for the first time that helicity has a huge impact on transfection efficiencies."

Earlier this year, Cheng's group developed a method of making helical polypeptides with positively charged side chains.

To test whether a helical polypeptide could be an efficient gene delivery agent, the group assembled a library of 31 helical polypeptides that are stable over a broad pH range and can bond to DNA for delivery. Most of them outperformed PLL and a few outstripped a leading commercial agent called polyethyleneimine (PEI), notorious for its toxicity although it is highly efficient. The helical molecules even worked on some of the hardest cells to transfect: stem cells and fibroblast cells.

"People kind of gave up on polypeptide-based materials for gene deliveries because PLL had low efficiency and high toxicity," Cheng said. "The polypeptide that we designed, synthesized and used in this study has very high efficiency and also well-controlled toxicities. With a modified helical polypeptide, we demonstrated that we can outperform many commercial agents."

The polypeptides Cheng and his co-workers developed can adopt helical shapes because the side chains are longer, so that the positive charges do not interfere with the protein's winding. The positive charges readily bind to negatively charged DNA, forming complexes that are internalized into cellular compartments called endosomes. The helical structures rupture the endosomal membranes, letting the DNA escape into the cell.

To confirm that the spiral polypeptide shape is the key to transfection, the researchers then synthesized two batches of the most efficient polypeptide: one batch with a helical shape, one with the usual random coil. The helical polypeptide far exceeded the random-coil polypeptide in both efficiency and stability.

"This demonstrates that the helicity is very important, because the polymer has exactly the same chemical makeup; the only difference is the structure," said Cheng, who also is associated with the Institute for Genomic Biology and the Beckman Institute for Advanced Science and Technology, both at the U. of I.

Next, the researchers plan to further explore their helical polypeptides' properties, especially their cell-penetrating abilities. They hope to control sequence and structure with precision for specific applications, including gene delivery, drug delivery, cell-membrane penetration and antimicrobial action.

The National Science Foundation and the National Institutes of Health supported this work. Fei Wang is a professor of cell and development biology and of bioengineering. Postdoctoral researchers Nathan Gabrielson, Lichen Yin and Dong Li and graduate student Hua Lu were co-authors of the paper.


Story Source:

The above story is based on materials provided by University of Illinois at Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University of Illinois at Urbana-Champaign. "Let's do the twist: Spiral proteins are efficient gene delivery agents." ScienceDaily. ScienceDaily, 17 December 2011. <www.sciencedaily.com/releases/2011/12/111215232603.htm>.
University of Illinois at Urbana-Champaign. (2011, December 17). Let's do the twist: Spiral proteins are efficient gene delivery agents. ScienceDaily. Retrieved April 2, 2015 from www.sciencedaily.com/releases/2011/12/111215232603.htm
University of Illinois at Urbana-Champaign. "Let's do the twist: Spiral proteins are efficient gene delivery agents." ScienceDaily. www.sciencedaily.com/releases/2011/12/111215232603.htm (accessed April 2, 2015).

Share This


More From ScienceDaily



More Health & Medicine News

Thursday, April 2, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Wound-Healing Laser Soon to Be a Reality Israeli Scientist

Wound-Healing Laser Soon to Be a Reality Israeli Scientist

Reuters - Innovations Video Online (Apr. 1, 2015) Israeli scientists says laser bonding of tissue allows much faster healing and less scarring. Amy Pollock has more. Video provided by Reuters
Powered by NewsLook.com
Liberia Sees Resurgence of Drug Trafficking as Ebola Wanes

Liberia Sees Resurgence of Drug Trafficking as Ebola Wanes

AFP (Apr. 1, 2015) The governments of Liberia and Sierra Leone have been busy fighting the menace created by the deadly Ebola virus, but illicit drug lords have taken advantage of the situation to advance the drug trade. Duration: 01:12 Video provided by AFP
Powered by NewsLook.com
Stigma Stalks India's Leprosy Sufferers as Disease Returns

Stigma Stalks India's Leprosy Sufferers as Disease Returns

AFP (Apr. 1, 2015) The Indian government declared victory over leprosy in 2005, but the disease is making a comeback in some parts of the country, with more than a hundred thousand lepers still living in colonies, shunned from society. Duration: 02:41 Video provided by AFP
Powered by NewsLook.com
7-Year-Old Girl Gets 3-D Printed 'robohand'

7-Year-Old Girl Gets 3-D Printed 'robohand'

AP (Mar. 31, 2015) Although she never had much interest in prosthetic limbs before, Faith Lennox couldn&apos;t wait to slip on her new robohand. The 7-year-old, who lost part of her left arm when she was a baby, grabbed it as soon as it came off a 3-D printer. (March 31) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins